Analgesia in the Perioperative Period

Use of Caudal Quadratus Lumborum Block with Ropivacaine as Part of an Opioid-Free Analgesic Protocol in Dogs Undergoing Orchiectomy: A Randomized Trial

In veterinary medicine, the use of loco-regional anesthesia techniques is increasing. The Quadratus Lumborum block (QL) is an interfascial loco-regional technique that involves the release of local anesthetic (LA) between the Quadratus Lumborum and the Small Psoas (Pm) muscle. The study aims to evaluate the effect of the QL block on reducing the total amount of opioids in dogs undergoing pre-scrotal orchiectomy. A group of 36 dogs was enrolled in a randomized blinded study. The animals were divided into two groups: 18 in the experimental group (QL) and 18 in the control group (C). The QL group received 0.4 mL kg-1 of ropivacaine 0.5% for each hemiabdomen (total amount of 3 mg kg-1 of ropivacaine, 1.5 mg kg-1 per side). The C group was brought into the operating room (OR) after receiving the same clipping as the QL group. In the intraoperative period, opioid consumption in the QL group was significantly lower than in the C group. No differences were found in the post-operative phase. No side effects were reported when performing the QL technique. The QL block performed at the level of L6 appears to be a valid approach to reducing opioid use in dogs undergoing orchidectomy with a pre-scrotal surgical approach.

Comparison between Ultrasonographic-Guided Temporal and Coronoid Approaches for Trigeminal Nerve Block in Dogs: A Cadaveric Study

The trigeminal nerve is responsible for innervating the periorbita. Ultrasound-guided trigeminal block is employed in humans for trigeminal neuralgia or periorbital surgery. There are no studies evaluating this block in dogs. This study aims to evaluate and compare two approaches (coronoid and temporal) of the trigeminal nerve block. We hypothesised superior staining with the coronoid approach. Thirteen dog heads were used. After a preliminary anatomical study, two ultrasound-guided injections per head (right and left, coronoid and temporal approach, randomly assigned), with an injectate volume of 0.15 mL cm-1 of cranial length, were performed (iodinated contrast and tissue dye mixture). The ultrasound probe was placed over the temporal region, visualising the pterygopalatine fossa. For the temporal approach, the needle was advanced from the medial aspect of the temporal region in a dorsoventral direction. For the coronoid approach, it was advanced ventral to the zygomatic arch in a lateromedial direction. CT scans and dissections were conducted to assess and compare the position of the needle, the spread of the injectate, and nerve staining. No significant differences were found. Both approaches demonstrated the effective interfascial distribution of the injectate, with some minimal intracranial spread. Although the coronoid approach did not yield superior staining as hypothesised, it presents a viable alternative to the temporal approach. Studies in live animals are warranted to evaluate clinical efficacy and safety.

Evaluation of lidocaine administration into the ovarian pedicle for the control of intraoperative and early postoperative pain during ovariohysterectomy in dogs

OBJECTIVE

To evaluate effects of lidocaine 2% administration into the ovarian pedicle on intraoperative nociception and early postoperative pain in dogs undergoing ovariohysterectomy.

STUDY DESIGN

Prospective, randomized, blinded clinical study.

ANIMALS

A total of 20 healthy adult female dogs of different breeds.

METHODS

Dogs were premedicated with acepromazine (0.02 mg kg-1) and morphine (0.5 mg kg-1) intramuscularly, anesthesia induced with propofol and maintained with isoflurane. Dogs were randomly assigned to be administered 2 mL of saline (group S) or lidocaine 2% (group L) into the mesovarium (1 mL each side). Heart rate (HR) and noninvasive systemic arterial pressure were recorded before surgery (T0), before (T1) and during ligation of the right ovarian pedicle (T2), before (T3) and during ligation of the left ovarian pedicle (T4). Rescue treatment (propofol) was administered if HR or systolic arterial pressure (SAP) increased by 20% compared with the previous time point. Pain, assessed with the Glasgow Composite Measure Pain Scale-Short Form (CMPS-SF) was recorded before premedication (baseline) and after extubation. Administration of postoperative rescue analgesia was recorded.

RESULTS

In group S, HR was higher at T2 than T1 (112 ± 18 versus 89 ± 21 beats minute-1, p = 0.001) There were no significant differences between treatments at any time. SAP was higher at T2 than T1 in group S (110 ± 12 versus 100 ± 10 mmHg, p = 0.031). SAP was higher in group S than group L at T3 (113 ± 12 and 91 ± 10 mmHg, respectively, p = 0.001). No dogs required propofol intraoperatively. All dogs required postoperative rescue analgesia. Compared with baseline, CMPS-SF increased 60 minutes after extubation (group S; p = 0.019, group L; p = 0.043).

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of lidocaine 2% into the mesovarium did not reduce intraoperative nociception and did not improve postoperative analgesia.

Sedation quality of alfaxalone associated with butorphanol, methadone or pethidine in cats injected into the supraspinatus or the quadriceps muscle

OBJECTIVES

The aim of this study was to compare the quality of sedation with three different anaesthetic protocols (alfaxalone combined with butorphanol, methadone or pethidine) administered intramuscularly in cats, and to evaluate the influence of the injection site (between supraspinatus and quadriceps muscles) on the onset and quality of sedation.

METHODS

A total of 151 cats were selected for this study. Cats were sedated with alfaxalone (3 mg/kg) combined with either butorphanol (0.3 mg/kg; n = 50), methadone (0.3 mg/kg; n = 53) or pethidine (5 mg/kg; n = 48). The combination was injected intramuscularly into the supraspinatus (n = 79) or quadriceps muscle (n = 72). The data included a scoring system for the quality of sedation and physiological parameters, such as heart rate (HR), respiratory rate, body temperature and occurrence of mydriasis, monitored during the first 30 mins of anaesthesia.

RESULTS

The opioid associated with alfaxalone influenced the overall sedation score, the degree of myorelaxation, the occurrence of mydriasis and HR. The overall sedation score was poorer with butorphanol than with methadone (P = 0.008), and butorphanol induced a lower degree of myorelaxation than methadone (P = 0.013). The injection into the supraspinatus showed better qualitative results for sedation and a faster onset time (in about 3 mins) than that into the quadriceps (P <0.001). HR decreased from baseline (P <0.001) and over time (P <0.001), mainly in cats of the butorphanol-supraspinatus and pethidine-quadriceps groups (P = 0.004). The occurrence of mydriasis was lower after butorphanol than after methadone and pethidine (P = 0.025), while the incidence of side effects did not differ among groups.

CONCLUSIONS AND RELEVANCE

All three protocols provided a good quality of sedation and allowed performing the scheduled procedure. Moreover, the injection into the supraspinatus muscle showed superior results in all the qualitative scores of sedation and quicker onset time than that into the quadriceps muscle.

Local and Regional Anaesthetic Techniques in Canine Ovariectomy: A Review of the Literature and Technique Description

Simple Summary

This review stems from a general trend of increasing attention toward surgical nociception in the veterinary field. Indeed, veterinarian anaesthetists are becoming more careful in relieving perioperative nociception, improving the analgesic protocols and therefore optimising surgical outcomes. Canine ovariectomy is a common surgical procedure with a moderate level of pain. Therefore, intraoperative analgesia is very important because pain causes various systemic inflammatory effects that slow patient recovery. This review aims to collect all recent information about local and regional anaesthetic/analgesic techniques in a review of the literature describing the technique utilised. In addition, the present review aims to provide practical guidelines for veterinary practitioners to improve the anaesthetic techniques in canine neutering through an overview of the available literature. In fact, the methods described, considering the relative simplicity of execution, can be used in daily routine practice.

Abstract

Canine ovariectomy is an elective surgery with a moderate level of pain. Despite its relative simplicity, it requires surgical pain management. This study aimed to collect all recent information about local and regional anaesthetic/analgesic techniques in a review of the literature describing the technique utilised. The various procedures described in this review use local anaesthetics to improve analgesia in the routine systemic anaesthetic protocol. The approach described in this paper is called multimodal analgesia and is used in addition to the normal standard anaesthetic protocol. These techniques proved effective in minimising responses to the surgical stimulus and ensured adequate intraoperative and postoperative analgesia. The routine use of multimodal analgesia is considered a useful alternative for pain management in canine ovariectomy, in that it minimises patient suffering, improves the recovery of rescue analgesia, increases drug savings, and improves animal outcomes. In addition, the use of these local and regional techniques ensures satisfactory analgesic coverage that lasts for the first hours postoperatively.

Τhe Effect of Opioid Administration on Cytologic and Histopathologic Diagnosis of Canine Cutaneous Mast Cell Tumors Treated by Surgical Excision

Mast cell tumor (MCT) is a frequent cutaneous tumor in dogs, with a variable biological behavior. Studies correlate cytologic and histopathologic features of MCTs with their biological behavior, prognosis, and response to treatment. The use of preoperative opioids is common in canine patients undergoing surgical removal of these tumors. Certain opioids can induce or downregulate mast cell degranulation and influence cancer progression. The aim of the present study was to investigate whether the administration of morphine or butorphanol during surgical excision of canine cutaneous MCTs affects their cytologic and histopathologic appearance, thus influencing cytologic and histopathologic grading. This was a prospective, blinded, randomized, cohort clinical study. Forty-five dogs with cutaneous MCTs were randomly allocated into three groups according to preanaesthetic medication: dexmedetomidine combined with morphine (group M) or butorphanol (group B) or normal saline (group C). Cytologic specimens and histopathologic samples were obtained both prior to and after surgery. Samples were graded according to Kiupel’s and Patnaik’s systems, examined immunohistochemically for Ki-67 protein (Ki-67) and c-kit proto-oncogene product (KIT) expression, and histochemically for argyrophilic nucleolar organizing regions (AgNORs). Based on both Kiupel’s and Patnaik’s systems, no statistically significant differences were noted concerning the number of cases with grading discrepancies in grades allocated prior to versus after surgery among the groups. The same applied for cytological grading and immunohistochemical and histochemical evaluation. It seems that administration of morphine or butorphanol as part of the preanesthetic medication for surgical removal of canine cutaneous mast cell tumors does not influence histopathologic and cytologic grading of MCTs.

2022 AAHA Pain Management Guidelines for Dogs and Cats

These updated guidelines present a practical and logical approach to the assessment and management of acute and chronic pain in canine and feline patients. Recognizing pain is fundamental to successful treatment, and diagnostic guides and algorithms are included for assessment of both acute and chronic pain. Particularly for chronic pain, capturing owner evaluation is important, and pain-assessment instruments for pet owners are described. Expert consensus emphasizes proactive, preemptive pain management rather than a reactive, "damage control" approach. The guidelines discuss treatment options centered on preemptive, multimodal analgesic therapies. There is an extensive variety of pharmacologic and nonpharmacologic therapeutic options for the management of acute and chronic pain in cats and dogs. The guidelines include a tiered decision tree that prioritizes the use of the most efficacious therapeutic modalities for the treatment of acute and chronic pain.

Effects of morphine on histamine release from two cell lines of canine mast cell tumor and on plasma histamine concentrations in dogs with cutaneous mast cell tumor

OBJECTIVE

To determine the effects of morphine on histamine release from 2 canine mast cell tumor (MCT) cell lines and on plasma histamine concentrations in dogs with cutaneous MCTs.

ANIMALS

10 dogs with cutaneous MCT and 10 dogs with soft tissue sarcoma (STS).

PROCEDURES

The study consisted of 2 phases. First, 2 canine MCT cell lines were exposed to 3 pharmacologically relevant morphine concentrations, and histamine concentrations were determined by an ELISA. Second, dogs with MCT or STS received 0.5 mg of morphine/kg, IM, before surgery for tumor excision. Clinical signs, respiratory rate, heart rate, arterial blood pressure, rectal temperature, and plasma histamine concentrations were recorded before and 5, 15, 30, and 60 minutes after morphine administration but prior to surgery. Data were compared by use of a 2-way ANOVA with the Sidak multiple comparisons test.

RESULTS

In the first phase, canine MCT cell lines did not release histamine when exposed to pharmacologically relevant morphine concentrations. In the second phase, no differences were noted for heart rate, arterial blood pressure, and rectal temperature between MCT and STS groups. Plasma histamine concentrations did not significantly differ over time within groups and between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

No significant changes in histamine concentrations were noted for both in vitro and in vivo study phases, and no hemodynamic changes were noted for the in vivo study phase. These preliminary results suggested that morphine may be used safely in some dogs with MCT.

Effects of a Heated Anesthesia Breathing Circuit on Body Temperature in Anesthetized Rhesus Macaques (Macaca mulatta)

This study evaluated the effects of using a heated anesthesia breathing circuit in addition to forced-air warming on body temperature in anesthetized rhesus macaques as compared with forced-air warming alone. Hypothermia is a common perianesthetic and intraoperative complication that can increase the risk of negative outcomes. Body heat is lost through 4 mechanisms during anesthesia: radiation, conduction, convection, and evaporation. Typical warming methods such as forced-air warming devices, conductive heating pads, and heated surgical tables only influence radiative and conductive mechanisms of heat loss. A commercially available heated breathing circuit that delivers gas warmed to 104 °F can easily be integrated into an anesthesia machine. We hypothesized that heating the inspired anesthetic gas to address the evaporative mechanism of heat loss would result in higher body temperature during anesthesia in rhesus macaques. Body temperatures were measured at 5-min intervals in a group of 10 adult male rhesus macaques during 2 anesthetic events: one with a heated anesthesia breathing circuit in addition to forced-air warming, and one with forced-air warming alone. The addition of a heated breathing circuit had a significant positive effect on perianesthetic body temperature, with a faster return to baseline temperature, earlier nadir of initial drop in body temperature, and higher body temperatures during a 2-h anesthetic procedure. Use of a heated anesthesia breathing circuit should be considered as a significant refinement to thermal support during macaque anesthesia, especially for procedures lasting longer than one hour.

Attitudes and practices of veterinarians in Australia to acute pain management in cats

Objectives

Up-to-date information on the current practices and attitudes of veterinarians in Australia to acute pain management in cats was sought in 2017–2018 in the first nationwide survey in over 20 years.

Methods

An online survey was created, consisting of 54 questions in four sections, with 18 feline-specific questions. Veterinarians throughout Australia were invited to participate in the survey through advertisements in the veterinary press, electronic and regular mail, and through in-clinic visits and promotional materials.

Results

A total of 614 veterinarians completed the survey, with 513 (83.6%) completing the feline-specific section. The demographics of the respondents of this survey were an accurate representation of the registered veterinarians in Australia at the time. Multiple different opioids and non-steroidal anti-inflammatory drugs (NSAIDs) were widely available in practices to manage pain, with analgesic efficacy reported as the primary factor influencing drug selection. Opioids were most commonly used in the preoperative period and NSAIDs were most commonly used postoperatively. Despite the wide availability in clinic (>99%), only 55% of respondents reported regularly using local anaesthetic techniques in cats. Pain assessment of hospitalised patients was primarily performed by veterinarians (91.1%); however, 84.7% of respondents did not routinely use a validated pain scale.

Conclusions and relevance

Veterinary practitioners in Australia are adequately equipped with analgesic medication to treat pain in their patients. In the management of acute pain in cats, they frequently use a multimodal approach and practice a variety of analgesic protocols. Based on the results of this survey, potential areas for improvement in feline pain management include an increase in duration of postoperative analgesia and more routine use of validated pain scales, performed by nurses and veterinarians alike, to assess individual analgesic needs.

2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats

Risk for complications and even death is inherent to anesthesia. However, the use of guidelines, checklists, and training can decrease the risk of anesthesia-related adverse events. These tools should be used not only during the time the patient is unconscious but also before and after this phase. The framework for safe anesthesia delivered as a continuum of care from home to hospital and back to home is presented in these guidelines. The critical importance of client communication and staff training have been highlighted. The role of perioperative analgesia, anxiolytics, and proper handling of fractious/fearful/aggressive patients as components of anesthetic safety are stressed. Anesthesia equipment selection and care is detailed. The objective of these guidelines is to make the anesthesia period as safe as possible for dogs and cats while providing a practical framework for delivering anesthesia care. To meet this goal, tables, algorithms, figures, and "tip" boxes with critical information are included in the manuscript and an in-depth online resource center is available at aaha.org/anesthesia.

Safety evaluation of the interchangeable use of robenacoxib in commercially-available tablets and solution for injection in cats

Background

Robenacoxib (Onsior™) is a non-steroidal anti-inflammatory drug developed for canine and feline use for the control of pain and inflammation. It is available as both tablets and solution for injection.

The objective of this study was to evaluate the safety of the interchangeable use of commercially available robenacoxib formulations when administered to cats orally using 6 mg tablets and subcutaneously using a solution for injection containing 20 mg/mL. Thirty-four naïve healthy 4-month old cats were enrolled in this 37-day study and were randomized to four groups (three robenacoxib and one control). One robenacoxib group received the maximum recommended dose (MRD) rate of each formulation, while the other two received two and three times this dose rate. The cats underwent three 10-day treatment cycles comprised of seven days of once daily oral administration followed by three days of subcutaneous administration. The third cycle was followed by an additional seven days of oral treatment. The control group received oral empty gelatin capsules or subcutaneous saline injections. Assessment of safety was based on general health observations, clinical observations, physical, ophthalmic, electrocardiographic and neurological examinations, clinical pathology evaluations, food consumption, body weight, and macroscopic and microscopic examinations. Blood samples were collected for toxicokinetic evaluation.

Results

Blood concentrations of robenacoxib confirmed systemic exposure of all treated cats. All cats were in good health through study termination and there were no serious adverse events during the study. There were no changes in body weight, food consumption, ophthalmic, physical or neurological examinations during the study. Treatment-related abnormalities were of low occurrence at all doses and included injection site changes (transient edema with minimal or mild, subacute/chronic inflammation histologically) and prolongation of the QT interval. These findings were consistent with previously observed findings in studies with robenacoxib administered separately orally or subcutaneously in cats. Thus, there were no adverse effects that could be attributed specifically to the interchangeable use of oral and injectable robenacoxib.

Conclusions

This 37-day laboratory study supports the safety of interchanging robenacoxib injection at a daily dose of 2 mg/kg with robenacoxib tablets at a daily dose of 1 mg/kg, or vice versa.

Evaluation of nalbuphine, butorphanol and morphine in dogs during ovariohysterectomy and on early postoperative pain

OBJECTIVE

To evaluate the effects of nalbuphine, butorphanol and morphine combined with acepromazine on intraoperative and early postoperative pain management in dogs anesthetized for ovariohysterectomy.

STUDY DESIGN

Prospective, randomized blinded clinical study.

ANIMALS

A total of 48 healthy female dogs of different breeds, aged 1-6 years, weighing (mean ± standard deviation) 14.5 ± 4.8 kg.

METHODS

Dogs were randomly assigned into four groups to be intravenously administered nalbuphine (0.5 mg kg^-1; group N0.5), nalbuphine (1.0 mg kg^-1; group N1.0), butorphanol (0.4 mg kg^-1; group B0.4) or morphine (0.2 mg kg^-1; group M0.2) combined with acepromazine (0.02 mg kg^-1) prior to propofol and isoflurane for anesthesia. Heart rate (HR), respiratory rate, systolic arterial pressure and rectal temperature (RT) were recorded at time points during anesthesia. A dynamic interactive visual analog scale applied in three phases (DIVAS I, II and III) and the modified Glasgow composite measure pain scale were used to assess pain before premedication and 1, 2, 3, 4, 5 and 6 hours after extubation. Administration of rescue analgesia was recorded.

RESULTS

At the left ovarian pedicle ligation, HR was higher in N1.0 than in B0.4 (p = 0.020). RT decreased significantly by the end of surgery in N0.5 (p = 0.043) and B0.4 (p = 0.010). Rescue analgesia was administered postoperatively over 6 hours to eight, seven, nine and 10 dogs in N0.5, N1.0, B0.4 and M0.2, respectively (p = 0.57). DIVAS II was higher in B0.4 than in N1.0 at 2 and 3 hours (p = 0.038 and p = 0.002, respectively) and N0.5 at 3 hours (p = 0.003).

CONCLUSIONS AND CLINICAL RELEVANCE

At the doses used, all premedication protocols provided insufficient intraoperative analgesia, with minimal clinical differences between groups. No premedication provided satisfactory analgesia in the first 6 hours postoperatively.

Comparison of perioperative analgesia using the infiltration of the surgical site with ropivacaine alone and in combination with meloxicam in cats undergoing ovariohysterectomy

Background

Infiltration of the surgical site with local anesthetics combined with nonsteroidal anti-inflammatory drugs may play an important role in improving perioperative pain control. This prospective, randomized, blinded, controlled clinical trial aimed to evaluate intraoperative isoflurane requirements, postoperative analgesia, and adverse events of infiltration of the surgical site with ropivacaine alone and combined with meloxicam in cats undergoing ovariohysterectomy. Forty-five cats premedicated with acepromazine/meperidine and anesthetized with propofol/isoflurane were randomly distributed into three treatments (n = 15 per group): physiological saline (group S), ropivacaine alone (1 mg/kg, group R) or combined with meloxicam (0.2 mg/kg, group RM) infiltrated at the surgical site (incision line, ovarian pedicles and uterus). End-tidal isoflurane concentration (FE’ISO), recorded at specific time points during surgery, was adjusted to inhibit autonomic responses to surgical stimulation. Pain was assessed using an Interactive Visual Analog Scale (IVAS), UNESP-Botucatu Multidimensional Composite Pain Scale (MCPS), and mechanical nociceptive thresholds (MNT) up to 24 h post-extubation. Rescue analgesia was provided with intramuscular morphine (0.1 mg/kg) when MCPS was ≥6.

Results

Area under the curve (AUC) of FE’ISO was significantly lower (P < 0.0001) in the RM (17.8 ± 3.1) compared to S (23.1 ± 2.2) and R groups (22.8 ± 1.1). Hypertension (systolic arterial pressure > 160 mmHg) coinciding with surgical manipulation was observed only in cats treated with S and R (4/15 cats, P = 0.08). The number of cats receiving rescue analgesia (4 cats in the S group and 1 cat in the R and RM groups) did not differ among groups (P = 0.17). The AUC of IVAS, MCPS and MNT did not differ among groups (P = 0.56, 0.64, and 0.18, respectively). Significantly lower IVAS pain scores were recorded at 1 h in the RM compared to the R and S groups (P = 0.021–0.018). There were no significant adverse effects during the study period.

Conclusions

Local infiltration with RM decreased intraoperative isoflurane requirements and resulted in some evidence of improved analgesia during the early postoperative period. Neither R nor RM infiltration appeared to result in long term analgesia in cats undergoing ovariohysterectomy.

Clinical evaluation of postoperative analgesia, cardiorespiratory parameters and changes in liver and renal function tests of paracetamol compared to meloxicam and carprofen in dogs undergoing ovariohysterectomy

Background

In veterinary medicine, the administration of nonsteroidal anti-inflammatory analgesics (NSAIDs) for the control of postsurgical pain in dogs and cats is common given the anti-inflammatory, analgesic, and antipyretic effects of these drugs. This study compared the serum biochemical changes and postoperative analgesic effects of paracetamol, meloxicam, and carprofen in bitches submitted to an ovariohysterectomy using the Dynamic Interactive Visual Analog Scale (DIVAS) and Pain Scale of the University of Melbourne (UMPS) scoring systems.

Methods

Thirty bitches of different breeds underwent elective ovariohysterectomies and were randomly assigned to one of three treatment groups: a paracetamol group [15 mg kg^-1 intravenous (IV)], a carprofen group (4 mg kg^-1 IV), and a meloxicam group (0.2 mg kg^-1 IV). All treatments were administered 30 minutes prior to surgery. Paracetamol was administered every 8 hours postoperatively for 48 hours total, while carprofen and meloxicam were intravenously administered every 24 hours. An evaluation of post-surgical pain was done with the DIVAS and the UMPS. The first post-surgical pain measurement was performed 1 hour after surgery and then 2, 4, 6, 8, 12, 16, 20, 24, 36, and 48 hours after surgery.

Results

All groups exhibited a gradual reduction in pain throughout the postoperative period in both scales; however, neither scale significantly differed between the three treatment groups (P > 0.05) during the 48 postoperative hours.

Conclusions

Paracetamol was as effective as meloxicam and carprofen for post-surgical analgesia in bitches subjected to elective ovariohysterectomy. The present study demonstrates that paracetamol may be considered a tool for the effective treatment of acute perioperative pain in dogs. Furthermore, this drug led to no adverse reactions or changes in the parameters assessed in the present study, indicating its safety.

Clinical Management of Pain in Rodents

The use of effective regimens for mitigating pain remain underutilized in research rodents despite the general acceptance of both the ethical imperative and regulatory requirements intended to maximize animal welfare. Factors contributing to this gap between the need for and the actual use of analgesia include lack of sufficient evidence-based data on effective regimens, under-dosing due to labor required to dose analgesics at appropriate intervals, concerns that the use of analgesics may impact study outcomes, and beliefs that rodents recover quickly from invasive procedures and as such do not need analgesics. Fundamentally, any discussion of clinical management of pain in rodents must recognize that nociceptive pathways and pain signaling mechanisms are highly conserved across mammalian species, and that central processing of pain is largely equivalent in rodents and other larger research species such as dogs, cats, or primates. Other obstacles to effective pain management in rodents have been the lack of objective, science-driven data on pain assessment, and the availability of appropriate pharmacological tools for pain mitigation. To address this deficit, we have reviewed and summarized the available publications on pain management in rats, mice and guinea pigs. Different drug classes and specific pharmacokinetic profiles, recommended dosages, and routes of administration are discussed, and updated recommendations are provided. Nonpharmacologic tools for increasing the comfort and wellbeing of research animals are also discussed. The potential adverse effects of analgesics are also reviewed. While gaps still exist in our understanding of clinical pain management in rodents, effective pharmacologic and nonpharmacologic strategies are available that can and should be used to provide analgesia while minimizing adverse effects. The key to effective clinical management of pain is thoughtful planning that incorporates study needs and veterinary guidance, knowledge of the pharmacokinetics and mechanisms of action of drugs being considered, careful attention to individual differences, and establishing an institutional culture that commits to pain management for all species as a central component of animal welfare.

Multimodal analgesia for treatment of allodynia and hyperalgesia after major trauma in a cat

Case summary

A 2-year-old polytraumatized male cat was admitted to a teaching hospital for correction of a defective inguinal herniorrhaphy. Upon arrival, the cat showed signs of neuropathic pain, including allodynia and hyperalgesia. Analgesic therapy was initiated with methadone and metamizole; however, 24 h later, the signs of pain continued. Reparative surgery was performed, and a multimodal analgesic regimen was administered (methadone, ketamine, wound catheter and epidural anesthesia). Postoperatively, the cat showed signs of severe pain, assessed using the UNESP-Botucatu multidimensional composite pain scale. Rescue analgesia was initiated, which included methadone, bupivacaine (subcutaneous wound-diffusion catheter) and transversus abdominis plane block. Because the response was incomplete, co-adjuvant therapy (pregabalin and electroacupuncture) was then implemented. Fourteen days after admission, the patient was discharged with oral tramadol and pregabalin for at-home treatment.

Relevance and novel information

Neuropathic pain is caused by a primary lesion or dysfunction in the nervous system and is a well-described complication following trauma, surgical procedures such as hernia repair, and inadequate analgesia. The aims of this report are to: (1) describe a presentation of neuropathic pain to highlight the recognition of clinical signs such as allodynia and hyperalgesia in cats; and (2) describe treatment of multi-origin, severe, long-standing, ‘mixed’ pain (acute inflammatory with a neuropathic component). The patient was managed using multiple analgesic strategies (multimodal analgesia), including opioids, non-steroidal anti-inflammatory drugs, locoregional anesthesia, co-adjuvant drugs and non-pharmacological therapy (electroacupuncture).

The effects of aging on hydromorphone-induced thermal antinociception in healthy female cats

Introduction:

This study aimed to evaluate the effects of aging on hydromorphone-induced thermal antinociception in cats.

Methods:

In a prospective, randomized, blinded, controlled design, 10 healthy female cats received each of the following treatments intramuscularly: hydromorphone (0.1 mg/kg) and 0.9% saline (0.05 mL/kg) with a 1-week washout between treatments at 6, 9, and 12 months of age. Skin temperature and thermal thresholds (TTs) were recorded before and up to 12 hours after injection. Data were analyzed using a repeated-measures linear mixed model (α = 0.05).

Results:

After saline treatment, TT was not significantly different from baseline at any time point for any age group. After hydromorphone treatment, TT was significantly higher than baseline at 6 months for up to 1 hour, and at 9 and 12 months for up to 4 hours. Peak TT at 6, 9, and 12 months were 50.4 ± 2.7, 50.9 ± 2.0, and 53.6 ± 2.0°C at 0.5, 1, and 1 hours, respectively. Mean TT was significantly higher after hydromorphone treatment when compared with saline treatment at 9 and 12 months for up to 4 hours but not at 6 months. Magnitude of antinociception was consistently larger at 12 months when compared with 6 months of age. Hydromorphone provided a shorter duration and smaller magnitude of antinociception at 6 months when compared with 9 and 12 months.

Conclusion:

Pediatric cats may require more frequent dosing of hydromorphone than adults.

ABSENCE OF ACUTE TOXICITY OF A SINGLE INTRAMUSCULAR INJECTION OF MELOXICAM IN GOLDFISH ( CARASSIUS AURATUS AURATUS): A RANDOMIZED CONTROLLED TRIAL

Meloxicam is a nonsteroidal anti-inflammatory drug with preferential cyclooxygenase-2 inhibitory activity. It is frequently used in veterinary medicine, including in fish species. The efficacy and safety of meloxicam, however, has not yet been reported in adult fish. The purpose of this study was to evaluate the acute toxicity of a single intramuscular injection of meloxicam in goldfish ( Carassius auratus auratus). Following 3 wk of acclimation, 32 goldfish were randomly assigned to two groups of 16 individuals. Fish from the treatment group received a single intramuscular injection of 5 mg/kg meloxicam, while the fish from the control group received a single intramuscular injection of a 0.9% sodium chloride solution using a similar volume (1 ml/kg). No external lesions, mortality, or modifications in behavior or position in the water column were noted during the following 72 hr. Three days after the initial injection, all fish were euthanized by immersion in a solution of tricaine methanesulfonate. Complete postmortem and histologic evaluations were performed for each fish. Hemorrhage and muscular necrosis were observed at the site of injection in fish from both groups. Multiple granulomas of undetermined etiology were detected in numerous organs from fish of both groups. No statistically significant differences were detected in regard to the lesions observed in these two groups. This study demonstrates that a single intramuscular injection of meloxicam at a dosage of 5 mg/kg does not cause acute toxicity in goldfish.

Efficacy and Safety of Injectable Robenacoxib for the Treatment of Pain Associated With Soft Tissue Surgery in Dogs

Background

Nonsteroidal anti‐inflammatory drugs (NSAIDs) are used routinely to control pain and inflammation after surgery in dogs. Robenacoxib is a cyclooxygenase‐2 selective NSAID.

Hypothesis/Objective

Assess the clinical efficacy and safety of an injectable formulation of robenacoxib in dogs undergoing surgery.

Animals

Three hundred and seventeen client‐owned dogs (N = 159 robenacoxib or N = 158 placebo).

Methods

In this prospective, multicenter, randomized, masked, placebo‐controlled, parallel‐group study, dogs received a SC injection of either robenacoxib, at a target dose of 2.0 mg/kg, or placebo once prior to surgery and for 2 additional days postoperatively. Pain assessments were performed using the short form of the Glasgow Composite Measure Pain Scale (CMPS‐SF). The primary efficacy variable was treatment success/failure, with failure defined as the need for rescue therapy to control pain or withdrawal of the dog from the study due to an adverse event.

Results

Significantly (P = .006) more dogs administered robenacoxib were considered treatment successes (108 of 151, 73.7%) compared to dogs given placebo (85 of 152, 58.1%). Total pain scores (P < .01), pain at the surgery sites (response to touch, P < .01), and posture/activity (P < .05) were significantly improved at 3, 5, and 8 hours postextubation in dogs receiving robenacoxib versus placebo.

Conclusions and Clinical Importance

Robenacoxib administered by SC injection prior to surgery and for 2 additional days postoperatively was effective and well tolerated in the control of postoperative pain and inflammation associated with soft tissue surgery in dogs.

Efficacy and safety of oral robenacoxib (tablet) for the treatment of pain associated with soft tissue surgery in client-owned dogs

Background

Non-steroidal anti-inflammatory drugs (NSAIDs) have been proven to be effective in controlling peri-operative pain in dogs. Robenacoxib is an NSAID with high selectivity for the cyclooxygenase (COX)-2 isoform. The objective of this study was to assess the efficacy and safety of an oral tablet formulation of robenacoxib in client-owned dogs undergoing soft tissue surgery. The study was a prospective, multi-center, randomized, masked, placebo-controlled, parallel-group clinical trial. A total of 239 dogs were included and randomly allocated in a 1:1 ratio to receive either robenacoxib or placebo. Each dog received an oral tablet administration of either robenacoxib, at a target dose of 2 mg/kg, or placebo once prior to surgery and for two additional days post-operatively. All dogs also received a pre-anesthetic dose of 0.2 mg/kg butorphanol (intravenous or intramuscular). Pain assessments were performed using the short form of the Glasgow Composite Measure Pain Scale. Robenacoxib was compared to the placebo group on a success/failure basis. Treatment failure was defined as the need for rescue therapy to control post-operative pain.

Results

Significantly (P = 0.019) more dogs administered robenacoxib were considered treatment successes (89 of 116, 76.72%) compared to dogs given placebo (74 of 115, 64.35%). The percentage of treatment failure was therefore 23.28% in the robenacoxib and 35.65% in the placebo group. The least squares mean total pain scores were significantly different between groups and in favor of robenacoxib at 3 and 5 hours (P < 0.05) and 8 hours post-extubation (P < 0.01). Pain at the surgery sites (response to touch) was also significantly improved at 3, 5 and 8 hours post-extubation in dogs receiving robenacoxib versus placebo (P < 0.01). In addition, a significant overall improvement in posture/activity was revealed with robenacoxib having lower scores versus placebo (P < 0.01). No significant differences between the robenacoxib and placebo groups in the frequency of reported adverse events were observed.

Conclusions

Robenacoxib by oral (tablet) administration was effective and well tolerated in the control of peri-operative pain and inflammation associated with soft tissue surgery in dogs.

[Perioperative pain therapy in dogs and cats - an overview]

Undermanaged pain leads to negative systemic effects that may greatly disturb our patients' welfare. Therefore, a pain assessment tool should be routinely implemented into clinical practice. Validated pain assessment tools are available for dogs and cats. Advanced analgesic therapy follows the principle of a multimodal approach. This means that different analgesic drugs, which act on different targets within the nociceptive pathway, are combined to achieve the desired analgesic effects. In addition to opioids, nonsteroidal anti-inflammatory drugs and local anaesthetics, α2-receptor-agonists, ketamine and gabapentin as well as different nonpharmacologic analgesic techniques are used within the framework of a multimodal analgesic plan.